There have been demands for light weight, thin, low power-consuming, high definition, large-area display devices for use in AV equipment like home-use television sets and in OA machines. Therefore, the development of large-area displays for actual applications has been carried out in respect of display devices such as cathode ray tube display (CRT), liquid crystal display (LCD), plasma display (PDP), electro-luminescence display (EL) and light emitting diode display (LED).
In particular, liquid crystal display devices are advantageous because they can have much smaller thickness (depth) and power consumption, and easily provide a full-color display compared to display devices of other types. For this reason, in resent years, liquid crystal display devices have been used in various fields, and large-area liquid crystal displays have been greatly expected.
However, when fabricating a large-area liquid crystal display device with a conventional structure, the ratio of defects such as disconnection of signal lines and defective pixels abruptly increase during the fabrication process. The increase in the defection ratio causes such a problem that the price of the liquid crystal display device rises. In order to solve this problem, a large-area liquid crystal display device has been fabricated by simply connecting a plurality of liquid crystal panels together.
However, in the large-area liquid crystal display device fabricated in this method suffers from drawbacks that the joint in a display formed by the liquid crystal panels is noticeable, and displayed images have degraded display quality. In order to obtain natural displayed images, it is necessary to render the joint in the display of the liquid crystal display panels less noticeable.
Therefore, as a method for making the joint in the display of a large-area liquid crystal display device less noticeable, the present inventors proposed to dispose three pixel electrodes corresponding to red (R), green (G) and blue (B) filters at positions which are separated from the connected section of the liquid crystal panels by the same distance in Japanese Publication of Unexamined Patent Application No. 146455/1996 (Tokukaihei 8-146455).
In a large-area liquid crystal display device fabricated in this method, as illustrated in FIG. 13, liquid crystal panels 101 include pixels 113 arranged in matrix form, and each pixel 113 includes three pixel electrodes 114 which corresponds to R, G and B filters and are arranged in the order R, G and B (hereinafter referred to as the RGB order) so as to be separated from a connected section 111 by substantially the same distance. More specifically, the three pixel electrodes 114 are aligned in a direction parallel to the connected section 111 (the Y-axis direction in FIG. 13) that is an up-and-down direction of a displayed image (for example, a building) on the display.
As shown in FIG. 14, the pixels 113 are driven by TFT elements 115 which are respectively connected to the pixel electrodes 114 corresponding to R, G and B. Specifically, the TFT elements 115 are connected to signal lines 117 and scanning lines 118 which are respectively insulated by insulating films 116. Each of the pixel electrodes 114 is independently driven by the TFT element 115.
In this structure, even when light passing through the color filters corresponding to the pixels 113 located adjacent to the connected section 111 is refracted or scattered in the connected section 111, the degree of color modulation is substantially uniform in the respective pixels 113. Therefore, the color balance of light does not vary with respect to light coming from a direction oblique to the pixels 113 near the connected section 111, thereby preventing regions of different color tones from being produced in the connected section 111. Consequently, the joint in the large-area liquid crystal display becomes less noticeable.
Thus, by joining two pieces of liquid crystal panels together and rendering the joint in the display less noticeable, it is possible to provide displayed images with high quality.
However, in the alignment of pixel electrodes according to the method of the above-mentioned publication, Japanese Publication of Unexamined Patent Application No. 146455/1996, the length of each signal line 117 becomes at least twice longer than that of a conventional structure. Therefore, the delay of an electric signal functioning as a drive signal for providing a displayed image in the signal line 117 increases, causing vicious effects on the displayed image.
More specifically, in a conventional active-matrix type liquid crystal display device performing line-sequential scanning, signal lines are provided along the Y-axis direction shown in FIG. 14. In such a device, scanning lines are provided along the X-axis direction shown in FIG. 14 that crosses at right angles with the Y-axis direction. As described above, the Y-axis direction is the up-and-down direction (vertical direction) of a displayed image, for example, a building on the display, and the X-axis direction is the lateral direction of the displayed image.
Meanwhile, in a liquid crystal display device fabricated according to the method disclosed in Japanese Publication of Unexamined Patent Application No. 146455/1996, the pixel electrodes 114 are driven by drive signals similar to those of the conventional active-matrix type liquid crystal display device. In this device, the signal lines 117 are arranged in a shape like a square bracket around the pixel electrodes 114 so that the signal lines 117 are provided along the Y-axis direction. Consequently, the length of each signal line becomes at least twice longer than that of the conventional structure. Hence, in a large-area liquid crystal display device, when the signal lines 117 are arranged in such a manner, electric signals are delayed, causing vicious effects on displayed images.
In addition, since the number of crossings where the scanning lines 118 intersect the signal lines 117 through the insulating films 116 therebetween increases, defects are likely to occur due to an electrical short circuit at the crossings.